1. Field of the Invention
The present invention relates to a glass ceramic material that has a deformation temperature at which reheat press-forming can be performed in a glass state and further has a thermal expansion coefficient of xe2x88x9210xc3x9710xe2x88x927 to 20xc3x9710xe2x88x927 (1/xc2x0 C.) on the basis of precipitation of a negative thermal expansion crystal by crystallization treatment after the forming; a glass ceramic product; and a process for producing the glass material.
2. Description of Related Art
In the optical communication technology field, at the present time, optical transmission members having a quartz fiber medium are mainly used. In various devices connected to the quartz fiber, such as a waveguide, a quartz substrate is also used. As requirements of a glass material used in optical members, such as various devices, it is important that a minute and highly precise pattern can be formed and that the glass material has a thermal expansion coefficient near the thermal expansion coefficient of the quartz material to which the glass material is to be connected, that is, 5xc3x9710xe2x88x927 (1/xc2x0 C.). Therefore, a quartz substrate obtained by grinding quartz glass and then forming a minute and a highly precise pattern therein is used.
However, in the grinding method, which gives a high precision, much time is required for grinding since the glass material of the substrate is brittle, and adjustment is necessary to avoid occurrences where a grinding edge is hit on the end of the substrate and damaged. Thus, the grinding method has problems, in that it takes much time to carry out this method and also in that the costs are high. A pattern-forming method based on reheat press-forming is effective, in which patterns having very high precision can be formed together at a low cost. However, conventional glass materials have a deformation temperature, Td, at which reheat press-forming can be performed in a glass state, but their thermal expansion coefficient xcex1 after the forming is greatly different from that of SiO2, that is, 5xc3x9710xe2x88x927 (1/xc2x0 C.). Conversely, even if materials have a thermal expansion coefficient a after the forming near to that of SiO2, that is, 5xc3x9710xe2x88x927 (1/xc2x0 C.), the materials do not have a deformation temperature, Td, at which reheat press-forming can be performed in a glass state. Specifically, BK-7, as a substrate material, has a thermal expansion coefficient xcex1 of 89xc3x9710xe2x88x927 (1/xc2x0 C.) and a deformation temperature Td of 630xc2x0 C.; thus, BK-7 is capable of being subjected to reheat press-forming. However, BK-7 has a thermal expansion coefficient that is largely different from that of quartz fibers. Substrates made of quartz (SiO2) and Miraclon PH-3, made by NGK Insulators, Ltd., have thermal expansion coefficients a of 5xc3x9710xe2x88x927 (1/xc2x0 C.) and xe2x88x924xc3x9710xe2x88x927 (1/xc2x0 C.) and deformation temperatures Td of 1700xc2x0 C. and 770xc2x0 C., respectively. These have a thermal expansion coefficient that is not very different from that of quartz fibers, but are not easily subjected to reheat press-forming.
Thus, an object of the present invention is to provide a glass material having a low deformation temperature when it is press-formed, and having a thermal expansion coefficient equivalent to that of quartz materials when it is finished into a product. Such optical members include members assembled into a given shape, using an ultraviolet ray hardening type resin adhesive. It is also desired that the glass material itself of such optical members has such a nature that it can transmit ultraviolet rays.
According to a first aspect of the present invention, a SiO2xe2x80x94Al2O3xe2x80x94Li2O component-based glass material is provided, and comprises, as its basic components, SiO2: 60-63 wt % (the symbol xe2x80x9cwt %xe2x80x9d means % by weight); Al2O3: 23-25 wt %; and Li2O: 4-5 wt %. Further, modifying components are also provided, including ZrO2: 1.5-2.5 wt %; TiO2: 0.5-2.5 wt %; MgO: 0.5-1.5 wt %; ZnO: 0.5-1.2 wt %; Na2O: 0.5-2.0 wt %; and K2O: 0.5-2.0 wt %. The glass material further comprises BaO: 0.5-1.0 wt %. Since this glass material can have a deformation temperature of 750xc2x0 C. or lower, it becomes easy to produce a glass product by reheat press-forming.
According to a second aspect of the present invention, a SiO2xe2x80x94Al2O3xe2x80x94Li2O component-based glass material is provided, which comprises, as its basic components, SiO2: 60-63 wt %; Al2O3: 23-25 wt %; and Li2O: 4-5 wt %. Modifying components of the glass material include ZrO2: 1.5-2.5 wt %; TiO2: 0.5-2.5 wt %; MgO: 0.5-1.5 wt %; ZnO: 0.5-1.2 wt %; Na2O: 0.5-2.0 wt %; and K2O: 0.5-2.0 wt %. The glass material further comprises CaO: 1.0-2.0 wt %.
According to a third aspect of the present invention, a SiO2xe2x80x94Al2O3xe2x80x94Li2O component-based glass material is provided, which comprises, as its basic components, SiO2: 60-63 wt %; Al2O3: 23-25 wt %; and Li2O: 4-5 wt % and, as its modifying components, ZrO2: 1.5-2.5 wt %; TiO2: 0.5-2.5 wt %; MgO: 0.5-1.5 wt %; ZnO: 0.5-1.2 wt %; Na2O: 0.5-2.0 wt %; and K2O: 0.5-2.0 wt %. The glass material further comprises B2O3: 0.01-1.0 wt %. These glass materials also make it easy to produce a glass product by reheat press-forming.
Preferably, the glass materials according to the first, second and third aspects of the present invention do not include P2O5.If the glass materials comprise P2O5, crystallization is excessively promoted, and controlling of the crystallization is difficult. For example, the thermal expansion coefficients may not be within the desired range.
According to a fourth aspect of the present invention, a glass ceramic material is provided comprising the glass material according to any one of the above 1st-3rd aspects, and having a thermal expansion coefficient in a range of xe2x88x9210xc3x9710xe2x88x927 to 20xc3x9710xe2x88x927 (1/xc2x0 C.). Thus, this glass ceramic material has a thermal expansion coefficient that is substantially the same as that of a quartz fiber or the like that is connected as an optical member. Therefore, the state of the connection is stable. As a result, the glass ceramic material is not exfoliated, communication is not interrupted and signals are not deteriorated.
According to a fifth aspect of the present invention, a glass ceramic material is provided, comprising the glass material according to any one of the 1st-3rd aspects, and having a crystallization ratio in a range of 30 to 50%. Since this glass ceramic material has a crystallization ratio within the range of 30 to 50%, this is a preferred material from the viewpoint of thermal expansion coefficient and shape precision. In other words, if the crystallization ratio is below 30%, the glass ceramic material having the desired thermal expansion coefficient cannot be obtained. If this ratio is over 50%, it is difficult to control the shape precision in the formed pattern, that is, the distribution of crystal phases, the size of the respective crystal phases, and so on. Thus, the shape precision is adversely affected.
According to a sixth aspect of the present invention, a glass material is provided, comprising the glass material according to one of the 1st or 3rd aspects, having a thermal expansion coefficient in a range of xe2x88x9210xc3x9710xe2x88x927 to 20xc3x9710xe2x88x927 (1/xc2x0 C.), and having ultraviolet ray transmissivity. Since this low thermal-expansion glass ceramic material can transmit ultraviolet rays, this material can be fixed on an optical member using an ultraviolet ray hardening type adhesive, for example, between a supporting substrate and a lid substrate.
According to a seventh aspect of the present invention, a glass ceramic material is provided, comprising the glass material according to any one of the 1st-3rd aspects, having a crystallization ratio in a range of 30 to 50%, and having ultraviolet ray transmissivity. This is suitable for reheat press-forming from the viewpoints of thermal expansion coefficient and shape precision, and can be finished into a product that can be fixed on an optical member using an ultraviolet ray hardening type adhesive.
According to an eighth aspect of the present invention, a glass product made of the glass material according to any one of the 1st-6th aspects is provided. This can be suitably used in, for example, a fiber array, a waveguide substrate, an optical lens, a reflector for a lamp, a light source for a lamp, or the like. The method for forming the glass material to obtain a glass product having a desired shape is preferably a reheat press method, but may be a grinding method.
According to a ninth aspect of the present invention, a process for producing a SiO2xe2x80x94Al2O3xe2x80x94Li2O component-based glass material is provided, comprising the steps of providing a glass material obtained by blending SiO2: 60-63 wt %; CaO: 1.0-2.0 wt %; Al2O3: 23-25 wt %; and Li2O: 4-5 wt %, as basic components, and ZrO2: 1.5-2.5 wt %; TiO2: 0.5-2.5 wt %; MgO: 0.5-1.5 wt %; ZnO: 0.5-1.2 wt %; Na2O: 0.5-2.0 wt %; and K2O: 0.5-2.0 wt %, as modifying components, with any one of BaO: 0.5-1.0 wt %, CaO: 1.0-2.0 wt %, and B2O3: 0.01-1.0 wt %; melting the blend and quenching the melted blend; press-forming the blend into a desired shape; and subjecting the product obtained in the above-mentioned step to a crystallization treatment to precipitate a negative thermal expansion crystal having a thermal expansion coefficient in a range of xe2x88x9210xc3x9710xe2x88x927 to 20xc3x9710xe2x88x927 (1/xc2x0 C.) According to this process, it is possible to provide a glass material having a low deformation temperature when it is press-formed, and having a thermal expansion coefficient equivalent to that of quartz materials when it is finished into a product, as described above. It is allowable to perform reheat press-forming as a primary step, and then perform the crystallization treatment, as a secondary step, after the forming, or to perform the crystallization treatment step and subsequently perform the forming step based on reheat press-forming.